1. Field of the Invention
The present invention relates to a method of grinding a rounded annular corner formed between a cylindrical portion of a workpiece and a shoulder portion adjacent to the cylindrical portion, and more particularly to a method of grinding the rounded annular corner of the workpiece by a grinding wheel whose rotation axis is arranged across the rotation axis of the workpiece.
2. Description of the Background
In FIG. 1 there is illustrated a conventional method of grinding a rounded annular corner Wc formed between a cylindrical portion Wa of a workpiece W and a shoulder portion Wb adjacent and perpendicular to the cylindrical portion Wa, wherein an apex portion Gp of a grinding wheel G is first positioned at a starting point Pa and is subsequently moved along a finish surface Sc of the rounded annular corner Wc toward a terminal point Pb to successively grind the rounded annular corner Wc and shoulder portion Wb of workpiece W. When the apex portion Gp of grinding wheel G has arrived at the terminal point Pb, the grinding wheel G is moved in a reverse direction at the terminal point Pb to return along the ground surface Sc of rounded annular corner Wc toward the start point Pa. During such a grinding process, it has been experienced that the grinding wheel G cuts into the shoulder portion Wb of workpiece W in its reverse movement at the terminal point Pb, resulting in grinding burn or seizure at the shoulder portion Wb of workpiece W. This problem is caused by the fact that immediately after reversed at the terminal point Pb, the return movement of grinding wheel G toward the starting point Pa is inevitably delayed due to a lapse of time for reverse feed of the grinding wheel and the return movement of workpiece W is also inevitably delayed due to a lapse of time for reverse feed of the workpiece. Since the feed screw shaft for the workpiece is longer than the feed screw shaft for the grinding wheel, the delay in reverse movement of the workpiece W becomes larger than that in reverse movement of the grinding wheel G. In the occurrence of such delays in relative reverse movement of the grinding wheel and the workpiece, the grinding wheel W is deviated from its return path toward the starting point Pa and cuts into the shoulder portion Wb of workpiece W.